It was from the latest episode of Gilmore Girls. Paris says that she is going to sleep with the other girls, since she is scared of being infected with the cold that Rory's caught. Rory then says something like "How very the l-word!"
there is a new programme on air the US at the moment called the L word and it is about lesbians, so it could be that.
It could be love, too, it would depend on the context. It is a popular construction in UK and can be made to fit any number of situations, like parents discussing getting a toddler to bed might say "shall we mention the B word?"